I have had a tank my entire life. I started with a 75 gallon that was maintained by my mother for 20+ years. I had it for 10 years before selling it and upgrading to a 200 gallon about 6 months ago. About 3 weeks ago I got 2 rope fish. 1 got out and was eaten by my cat on the 3rd day. I got another about 4 days later. Tonight I got home and one of them “Wiggles” was hanging out in the floating plants with his tail straight down and it looked like he was gasping for air and ignoring the worms I gave him. I thought he might be stuck so I moved the plants and he swam away awkwardly. Like his back end isn’t working. I looked over him closely when he came back to the top and got back in the plants. He has no other signs or symptoms that I can see. No swelling, no discoloration, nothing. Nitrates are 0 ph is 7 and water has plenty of oxygen. Help?